# std::experimental::find_first_set, std::experimental::find_last_set

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< cpp‎ | experimental‎ | simd

Defined in header `<experimental/simd>` |  |
template< class T, class Abi > int find_first_set( const simd_mask<T, Abi>& k ); | (1) | (parallelism TS v2)
template< class T, class Abi > int find_last_set( const simd_mask<T, Abi>& k ); | (2) | (parallelism TS v2)

1) Returns the lowest index `i` where k[i] is true.
2) Returns the greatest index `i` where k[i] is true.

The behavior is undefined if any_of(k) is false.

### Parameters

k | - | the `simd_mask` to apply the reduction to

### Return value

An int in the range `[`​0​`,` simd_size_v<T, Abi>`)`.

### Example

Run this code

    #include <cstddef>
    #include <experimental/simd>
    #include <iostream>

    namespace stdx = std::experimental;

    template<typename Abi>
    int find(stdx::simd_mask<Abi> const& v)
    {
        if (stdx::any_of(v))
            return find_first_set(v);
        return -1;
    }

    int main()
    {
        stdx::simd_mask<short> a{0};
        a[2] = a[a.size() - 2] = 1;

        for (std::size_t i = 0; i < a.size(); ++i)
            std::cout << a[i] << ' ';
        std::cout << '\n';

        std::cout << "find_first_set: " << stdx::find_first_set(a) << '\n';
        std::cout << "find_last_set: " << stdx::find_last_set(a) << '\n';
        std::cout << "find: " << find(a) << '\n';
        a[2] = 0;
        std::cout << "find: " << find(a) << '\n';
        a[a.size() - 2] = 0;
        std::cout << "find: " << find(a) << '\n';
    }

Possible output:

    0 0 1 0 0 0 1 0
    find_first_set: 2
    find_last_set: 6
    find: 2
    find: 6
    find: -1

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